Terminal for circuit elements



Sept. 22, 1931. H, G, RICHTER 1,824,447

TERMINAL FOR ICTRCUIT ELEMENTS Filed April 27, 1929 w `mmmm`mw llllllllll'llllllllllllllllllllllllllfI 1 i .v. M mmwmnm- TTOR EY Patented Sept. 22, 1931 UNITED STATES PATENT OFFICE Application led April 27, 1929. Serial No. 358,730.

My invention relates to certain improvements in applying terminals to circuit wires, circuit elements and the like, and while not limited in its use, has particular application to the terminals of wire-wound high resistance units.

Among the principal objects of the invention may be mentioned the production of a simple, effective and economical means for insuring perfect electrical contact in the application of terminals, which must be applied cold and secured by clamp pressure, without the aid of soldering.

Strict observance of the above requirellments is necessary, for example where the wire of resistance units to which terminals are to be applied, is so very fine it will not withstand eitherv rough treatment or high temperature, to which it is usually subjected when the terminals are soldered.

The particular type of high resistance unit for which the present improvement is specially designed is illustrated and described in United States Letters Patent No.

1,697 ,416, granted January 1, 1929, to Electrad, Inc., as my assignee.

As described in the patent referred to, the purpose there is to produce a unit of the highest possible resistance value, per inch of length, and to this end, an extremely fine resistance wire is employed, which is spirally wound on a core of insulating material, such as asbestos cord, or like material, with or without a metallic core.

The 'advantage of using asbestos cord is that the resistance wire, as it is wound thereon, becomes suiiiciently embedded in the cord to hold against displacement and also to escape fracture or other injury from rough 40 handling, accidental blows, etc., but as thus constructed, presents considerable difficulty to the successful application of the necessary terminals for connection in circuit. Soldering has proved ractically impossible and contact lugs, coldp closed on the wire, under pressure, are not entirely successful, as good electrical contact isv not always secured.

To remedy this difficulty tests made have shown that if a thin layer of lead or like material is interposed between the above described wire-wound resistance and the coldclosed clamp lugs of the terminals, perfect electrical contact results.

. A preferred embodiment of the invention 1s illustrated in the accompanying drawings 55 but I do not wish to be understood as limiting myself to the same, as various changes may be made therein without departing from the spirit and scope of the invention as outlined in the appended claims.

In the drawings- Fig. 1 is a view in elevation of a resistance unitconstructed in accordance with the present invention; f

Fig. 2 is a detail view, with the terminals 65 removed and a portion of the outer insulatmg covering broken away;

Fig. 3 shows the unit with the lead covering applied to the ends, preparatory to applying the terminals, and

Fig. 4 is a detail view on an enlarged scale of the completed connection, the terminal being shown in section. e v

Referring to the drawings, 1 represents a suitable core, which may consist of asbestos cord or like material, with or without a copper Wire or other metallic center.

Spirally wound on the core`1, there is a resistance wire 2, which, as wound, becomes sufficiently embedded in the yielding surface of the asbestos to be held properly spaced and protected against fracture or other injury from accidental blows, rough handling, etc.

Covering the resistance wire, thus wound, 8 there is an outer protecting envelope or sleeve 3, of insulating material, which terminates short of the ends of the wire leaving such ends exposed, as illustrated in Fig. 2, for attachment of the terminals. o

Before the terminals are attached, a covering of lead or other suitable material 4, is applied to the exposed ends of the wire, as A best shown in Fig. 3. Preferably a lead sleeve would be used for this purpose, but, owing to the diflculty and cost of producing such sleeves, I employ instead, a comparatively fine lead wire, which is spirally wound over the exposed ends of the resistance wire 100 projecting from opposite ends of the insulated body portion thereof.

To assist 1n winding on the lead wire and give it anchorage, the Winding i s started on the outer insulating covering, as 1nd1cated at A 5, and continued until the exposed end of the resistance wire is reached and completely covered.

Thus prepared, the resistance unit is ready for the attachment of the terminals' 6, 6, which may be of any suitable form but are preferably each provided with two sets of clamp lugs, one set or pair 7 7 being shaped and spaced to be cold-closed over the leadcovered end of the resistance wire; the other n pair 8, 8, being designed to be` similarly closed over that portion of the outer insulatg envelope covered by the lead wire wrapping.

In closing the clamp lugs -to secure the terminals in position, the soft yielding lead is forced into intimate contact with the fine resistance wire, making good electrical con-- tact, without displacing or injuring the Wire and completely enclosing the same to further protect it as it is later 'handled in shipment, sale and use.

the important advantages of the invention will be apparent from the foregoing description, it will not be necessary to elaborate them in further detail.

` Having thus described my invention, what I claim is:

1. A resistance unit comprisin a resistor element having a covering of insu ation suitably proportioned to leave the ends of the resistor exposed, a Winding of soft metal wire covering the exposed ends of the resistor, and terminal clips, each having two pairs of lugs, one pair clamping the insulation covering of the resistorand the other pair clamping the soft metal covered end thereof. l

2. A resistance unit comprising a resistor element having a covering of insulation suitably proportioned to leave the\ ends of the resistor exposed, a single layer winding of soft metal wire closely wound over the ends of the insulation and the exposed ends of the resistor, and terminal clips, each having two pairs of lugs, one

pair clamping the soft metal covered end o the insulation and the uother air clamping the sot metal covered end o the resistor.` I

I ax my signature.

mNRY G. RECHTER. 

